Wood expands with moisture content differently in the three basic dimensions.

The smallest change is usually along the length of the board. The next largest is perpendicular to the growth rings, followed by tangential to the growth rings.

Boiled down, consider a board that is quarter sawn (the grain is exactly vertical, running from one face of a board to the other). Usually a quarter sawn board displays the least amount of expansion across its width, this is perpendicular to the grain (case #2 above)

Plain sawn wood falls into case #3 and usually is the worst.

A once flat board (or glue-up of boards) warps when the moisture content is different on one side versus the other. Not much can be done to keep a board flat when this happens. For a cutting board, this happens when the board is left sitting in a puddle of water on the counter. Feet on the bottom of the board to keep it elevated above any wet counters helps here.

For a board that is evenly wet on both sides, the grain orientation comes into effect. If one side expands more with moisture than the other, the board will warp.

Now back to your question. Since your boards have been glued (there is moisture in the glue), give them plenty of time to dry out before judging. Ideally you want the direction of the grain all going in the same direction. This way, the entire cutting board will always move the same amount on both sides (and hopefully not warp).

I made an attempt at an “indestructible” end grain cutting board by trying to maximize all the ways to make sure the grain of the various pieces are in alignment. So far, so good.The project link has some pictures which may help explain some of this better 8^)

In my opinion, Grant is right. Typically the majority of warping is not from construction details, but from the wood getting wet on only one side. The grain alignment really is more important for the glue joints not being forced apart over the long term.

I might get skewered for my response – but I don’t buy into the flip every other board to prevent warping. I especially don’t buy into it for something as small as a cutting board. I believe a cutting board, of any construction type, is much more likely to warp by being mistreated than by poor construction.

Now I do say “poor construction” with tongue in cheek in that if you start with lumber that is not flat or otherwise properly prepared, then yes – a cutting board might warp. You can’t clamp a twisted/cupped/warped/etc. board into a nice, well constructed cutting board – it’s junk in, junk out in that instance.

It might just be luck (I don’t think so) – but I make and sell a lot of cutting boards and the only ones I have ever been called about being warped is because they have been left sitting in a puddle of water, once when it was actually submerged in a sink of dishwater or it was stored in a sun-drenched window sill.. That’s not to say I don’t pay attention to grain direction – but I pay more attention to the look of the board.

I can only speak to my experience and someone else may have a different experience and I can’t give you a scientific reason/rebuttal for why it’s not been a problem for me.

If you are consistently having a warping issue something might be askew in the lumber you are using or in technique.

I am also in the camp that your can over-clamp a project. You don’t have to make the clamps “gorilla” tight.

I don’t consider that at all and have zero trouble with end grain boards warping like flat-sawn deck.

I’m concerned with the pattern in the end grain. You can get some fantastic effects just by planning how the grain will look. Since you can choose whether or not to flip the pieces end-to-end before the second glue-up, you increase your design capability tremendously by paying attention to how the grain will look.

Here’s twist: Don’t flip end-to-end, but roll every pair of blocks toward each other. You can get some really great arches running all the way down the board if the growth rings are consistent throughout the board.

It’s all in the planning with end grain boards. You can make a stunning board or a blah one depending on your grain orientation and the order of your initial glue-up.

thanks for all of the responses. After glue up, I typically keep clamped, in doors over night. After unclamping, its on to the drum sander. I sand both sides smooth and fllat with 80 grit paper. Usually I sand a bunch of boards at same time. The following day, I switch to 120 grit. Some, not all of the boards, appear to have been warped. When I run it through the sander the middle will have a high point (or low, depending on which side) compared to the corners. So now I am stuck sanding and making it flat all over again. This is very frustrating.

I have made sure my drum is level, the boards are perfectly flat after the 80 sand. For some reason a few of the boards don’t like me and are warping. Any help would be appreciated. Thanks

Not sure what’s causing your warping. Like you, I keep my boards in the clamps overnight. But I don’t go straight to the sander right after unclamping. I generally let my boards sits for another 24 hours or more before going to the planer or sander.

Are you sanding so much that you are creating heat on the boards from the sander?

Heat IS an issue when sanding end grain boards. When doing the cleanup on the DS, I’ll get everything flat first with coarse (36 or 80 grit). I’ll let it sit for at least an hour after that to cool. I’ll do the fine sanding (120-180) the next day.I do notice that the boards will begin to warp as they heat up so I’ll always flip the board for each pass through the sander (which helps, but not completely).

Note that this warping is temporary. Any sanding before the glue is 100% dry and the wood is at equilibrium will potentially allow for warping in the future.